In a silver halide photographic light-sensitive material, the silver halide emulsion layer or some other layer is often colored for the purpose of absorbing light of a specific wavelength.
For example, in situations where it is necessary to control the spectral composition of the light incident at a silver halide emulsion layer, a colored layer is provided on the side of the emulsion layer on the photographic light-sensitive material that is away from the base. This kind of colored layer is called a filter layer (U.S. Pat. Nos. 2,527,583, 2,952,566, etc.).
In the case where there are a plurality of photographic emulsion layers such as in a multilayer color light-sensitive material, filter layers may be positioned between them.
Further, to prevent image blurring, i.e., "halation", a colored layer is provided between the emulsion layer and the base, or at the surface of the base opposite the emulsion layer. Halation occurs due to light scattering resulting from light passing through the emulsion layer or occurs after transmission from light being reflected at the interface between the emulsion layer and base, or at the surface of the light-sensitive material on the opposite side to the emulsion layer, and then again entering the emulsion layer. Such a colored layer is called an antihalation layer. In the case of a multi-layer color light-sensitive material, antihalation layers may be placed between the respective layers (U.S. Pat. Nos. 3,488,195, 3,575,704, etc.).
Moreover, in order to prevent a reduction in image sharpness due to scattering of the light in the emulsion layer (this phenomenon is generally called irradiation), the emulsion layer may be colored. Such colored emulsion layers are called "irradiation preventing layer" (U.S. Pat. No. 4,078,933, JP-B-51-46607) (the term "JP-B" as used herein means an "examined Japanese patent publication").
The layers colored in this way mostly comprise a hydrophilic colloid, and so normally a water soluble dye is incorporated into the layer to effect coloration. This dye needs to satisfy the following conditions.
(1) It must have an appropriate spectral absorption corresponding to the particular usage objectives.
(2) It must be photographically chemically inert. That is to say, there must be no adverse chemical effects on the performance of the silver halide photographic emulsion layer, such as a reduction in sensitivity, fading of the latent image or fogging.
(3) It must be decolored or lightened in the photographic treatment process, and there must be no residual color detrimental to the photographic light-sensitive material following treatment.
Considerable efforts have been made by those skilled in the art to discover dyes which meet these conditions. Processed dyes include oxonol dyes having a pyrazolone or barbituric acid nucleus, oxonol dyes, azo dyes, azomethine dyes, arylidene dyes, styryl dyes, triarylmethane dyes, merocyanine dyes and cyanine dyes.
However, among these dyes there are some which have little effect on the photographic emulsion itself but in the case of a spectrally-sensitized emulsion have the disadvantage of lowering sensitivity due to desorption of the sensitizing dyestuff, as well as spectral sensitization to unnecessary regions.
Again, insufficient decoloration or lightening can occur following treatment, as a result of the speeding-up of the developing treatment carried out in recent years. In order to resolve this problem, the use of dyes that are highly reactive with bisulfite ion has been proposed. However, the use of such dyes results in an insufficiently stable photographic film. More specifically a reduction in image density occurs with the passage of time and thus the desired photographic effect is not obtained.
Furthermore, in methods which utilize such water-soluble dyes, it is not possible to completely prevent diffusion of the dye contained in a specific layer, into other layers. Therefore, adverse effects are often exerted on other layers, and thus a so-called "discrete-layer dyeing technique" is strongly desired.
It is well-known that a leuco-dyestuff added to a silver halide light-sensitive material will be oxidized upon development to produce a developed dyestuff. However, the concept of adding a leuco-dyestuff which has already been developed and then decoloring or lightening this at the time of the photographic processing treatment is totally unknown.